Cylinders for air-cooled reciprocable piston internal combustion engines

ABSTRACT

In an air-cooled reciprocable piston engine having at least two adjacent cylinders with parallel longitudinal axes and transverse fins, in which adjacent fin portions of two adjacent cylinders are provided with straight substantially parallel edges defining therebetween a narrow gap while the ends of said straight edges merge by curved portions curved in the direction toward the axis of the pertaining cylinder with the segment-shaped remainder of the pertaining fins, tie rod means being located between adjacent curved portions of respectively pertaining fins of two adjacent cylinders.

United States Patent Howe 451 May 2,1972

[54] CYLINDERS FOR AlR-COOLED RECIPROCABLE PISTON INTERNAL COMBUSTIONENGINES [72] Inventor: Hans-Ulrich Howe,

forst, Germany Klockner-I-IumboIdt-Deutz Aktiengesellschaft,Cologne-Deutz, Germany Dec. 8, 1970 Bensberg-Franken- [73] Assignee:

22 Filed:

v [21] App]. No.: 96,212

[30] Foreign Application Priority Data Dec. 10, 1969 Germany ..P 19 61803.2

[52] U.S. Cl. ..l23/41.69, 123/59 R, 123/193 CH, 123/ 195 [51] Int. Cl...F02f l/06, F02f 1/30 [58] Field of Search ..123/41.69, 193 C, 193 CH,195 R, 123/59 R, 59 A, 59 B [5 6] References Cited UNITED STATES PATENTShm MW 2,608,962 9/1952 Kloss et al ..l23/4l.69

YIIIIIIIIIIIIIIIIIII 'I/I/IIIIIIII/IIIIIIIII 2,883,997 4/1959 Langmaier..l23/193 C FOREIGN PATENTS OR APPLICATIONS 899,161 5/1945 France 123/41.69

829,703 7/1938 France ..123/41.69

942,058 4/1956 Germany ..123/41.69

871,917 7/1961 Great Britain 123/41 .69

Primary Examiner-Al Lawrence Smith Attorney-Walter Becker ABSTRACT In anair-cooled reciprocable piston engine having at least two adjacentcylinders with parallel longitudinal axes and transverse t'ms, in whichadjacent fin portions of two adjacent cylinders are provided withstraight substantially parallel edges defining therebetween a narrow gapwhile the ends of said straight edges merge by curved portions curved inthe direction toward the axis of the pertaining cylinder with thesegment-shaped remainder of the pertaining fins, tie rod means beinglocated between adjacent curved portions of respectively pertaining finsof two adjacent cylinders.

3 Claims, 3 Drawing Figures Patented May 2, 1972 2 Sheets-Shut 1 FIG]Patented May 2, 1972 2 Sheets-Sheet 2 FIG. 1a

CYLINDERS FOR AIR-COOLED RECIPROCABLE PISTON INTERNAL COMBUSTION ENGINESThe present invention relates to an air-cooled multicylinderreciprocable piston engine with cylinders arranged in series andequipped with transverse fins.

With air-cooled reciprocable piston cylinders equipped with transversefins, it is customary in order to assure a sufficient cooling, to designthe cooling ribs of the cylinder, especially adjacent the cylinder head,as high as possible. The preferred circular shape of the fin contour is,in order to obtain a compact construction, somewhat flattened withserially arranged cylinders and, more specifically, in the region wheretwo adjacent cylinders are closest to each other. This means a reductionin the height of the fins in the said region. A further interruption ofthe circular shape of the fin contour is caused by cutouts or recessesfor the passage of the cylinder head connecting screws. These screwshave to be arranged as close as possible to the cylinder wall in orderto reduce the bending moment in the bottom of the cylinder head betweenthe cylinder head sealing surface and the point of attack of theconnecting screws.

The above mentioned various interruptions of the radial circumferentialcontour of the fins affects the strength of the cylinder and frequentlyresult in deformations, especially bends within the region of therecesses. As a result thereof, a non-uniform support (Tragbild) of thepiston is obtained. Therefore, it is the tendency to maintain thesedeformations in possibly narrow limits by special designs of thecylinders.

According to German Pat. No. 964,820 it is known to counteract thedeformation of the cylinder caused by recesses in the fins within theregion of the tie rods, by providing slots extending parallel to thecylinder axis between the recesses for the tie rods and in this way tomodify the deformations into a possibly uniform polygon so that a moreeven supporting structure of the piston will be obtained.

It has also been suggested in the thermally and mechanically highlystressed end of the cylinder adjacent the cylinder head not to interruptthe fins and to provide bores in the ribs for passing the connectingscrews therethrough. Inasmuch as these bores are difficult to cast, itis preferred to produce said bores mechanically, i.e., by drilling. Suchdrilling, however, has the drawback that the drill when cutting througheach individual rib has to cut twice through the hard outer cast skinwith the white solidified marginal zone. This is very hard on the drilland therefore considerably reduces the life of the drill. For thisreason, only the upper third, or one-half of the fins is drilled,whereas the lower two-thirds or one-half of the fins have their recessescast into the fins.

It has furthermore been suggested to keep the deformation of thecylinder within small limits by making the walls of the cylinder ofdifferent thickness, and more specifically by dimensioning those wallsthicker which contain the recesses for the passage of the screws, whilethose wall areas of the cylinder which are located between two screwsare thinner than the first mentioned walls.

It is, therefore, an object of the present invention, so to design thefin equipped cylinder that deformations of the cylinder within therecesses provided in the fins will practically be avoided.

This object and other objects and advantages of the invention willappear more clearly from the following specification, in connection withthe accompanying drawing, in which:

FIG. 1 diagrammatically illustrates a view of a cylinder pertaining to areciprocable piston engine.

FIG. 1a is a section along along the line lala of FIG. 2.

FIG. 2 is a top view of the cylinder shown in FIG. 1 while illustratingin dot-dash lines the contour of an adjacent cylinder.

An air-cooled multi-cylinder reciprocable piston engine with cylindersarranged in series and equipped with fins is, according to the presentinvention, characterized in that each two adjacent cylinders includingthe pertaining cylinder heads are, by means of a tie rod common theretoand located between said cylinders or by means of a plurality of tierods,

connected to the crank housing, and is furthermore characterized in thatthe cooling fins, especially those of the working cylinders have withinthe region of the tie rod or tie rods approximately semicircularrecesses of only slight depth, the line of confinement of which extendscontinually.

In view of this design, the original fin contour is practically retainedso that no' material deformation of the cylinder will occur as a resultof the forces exerted by the connecting screw, and furthermore a uniformcooling will be assured.

In view of the location of the tie rods at the end of the separating gapbetween two adjacent cylinders,'not only will the recess in the fins andthereby the local weakening of the cylinder be only slight, but it willalso be assured in an advantageous manner that the cooling air flow isdevided and deviated to the cylinder walls. It is a well known fact thatotherwise, in view of the separating gap between two adjacent cylinders,a portion of the cooling air is lost without doing any useful work.

According to a further feature of the invention, the recess in saidribsor fins in the region of the tie rods are precast so that a veryeconomical manufacture will be obtained.

Referring now to the drawing in detail, FIG. 1 shows a cylinder 1 withtransverse fins, comprising the fin-equipped section 2 and the lowershank portion 3 which is free from fins. FIG. 2 shows the circularsealing surface 4 of cylinder 1 for engagement with a correspondingsealing surface of the cylinder head. The circular shape of the fincontour 5 shows flat portions 6 at two sections located opposite to eachother, in order to reduce the distance between two adjacent workingcylinders and to thereby obtain a compact structure. Recesses 8 definedby a flat are having a radius r are provided in the fin contour for thetie rods 7. These recesses 8 gradually merge through rounded portions 9with the contour 5 of the fins.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular showing in the drawing, but alsocomprises any modifications within the scope of the appended claims.

What I claim is:

1. In an aircooled reciprocable piston engine with crank case: twocylinders having their longitudinal axes arranged parallel to each otherand respectively being provided with transverse fins extending aroundthe respective cylinder, those parts of at least some of said fins whichrespectively pertain to said two cylinders and are located adjacent toand opposite each other having substantially straight edge portionsextending at a substantially right angle with regard to the planepassing through the said parallel axes of said two cylinders, saidstraight edge portions defining with each other a relatively narrow gap,each end of each straight edge portion of each fin merging with arelatively large rounded portion of the same fin through a relativelyshort curved portion curved inwardly toward the interior of thepertaining cylinder, and tie rod means common to and arranged betweentwo adjacent ones of said inwardly curved portions for tieing saidcylinders to their cylinder heads and the crank case pertaining thereto.

2. An arrangement according to claim 1, in which said relatively shortcurved portions within the region of said tie rod means are pre-cast.

3. An arrangement according to claim 1, in which the depth of saidrelatively short curved portion is rather slight with regard to itswidth.

1. In an air-cooled reciprocable piston engine with crank case: twocylinders having their longitudinal axes arranged parallel to each otherand respectively being provided with transverse fins extending aroundthe respective cylinder, those parts of at least somE of said fins whichrespectively pertain to said two cylinders and are located adjacent toand opposite each other having substantially straight edge portionsextending at a substantially right angle with regard to the planepassing through the said parallel axes of said two cylinders, saidstraight edge portions defining with each other a relatively narrow gap,each end of each straight edge portion of each fin merging with arelatively large rounded portion of the same fin through a relativelyshort curved portion curved inwardly toward the interior of thepertaining cylinder, and tie rod means common to and arranged betweentwo adjacent ones of said inwardly curved portions for tieing saidcylinders to their cylinder heads and the crank case pertaining thereto.2. An arrangement according to claim 1, in which said relatively shortcurved portions within the region of said tie rod means are pre-cast. 3.An arrangement according to claim 1, in which the depth of saidrelatively short curved portion is rather slight with regard to itswidth.